1. Field of the Invention
This invention relates generally to spacer fabrication, and is well suited to forming spacers in a NAND flash memory array.
2. Background Art
The semiconductor market has been undergoing extensive growth over the past few decades. This trend is expected to continue for the foreseeable future since a large portion of this market is the memory segment. The memory segment can be broadly categorized into two classes, namely volatile memory and non-volatile memory. Volatile memory such as SRAM and DRAM lose their data content when the power supply is removed. In contrast, non-volatile memories such as EEPROM and flash memories maintain their data content after the power supply has been removed.
Non-volatile memories offer particular advantages, and thereby support a wide range of applications including computer, automotive and consumer electronic devices. Flash memory is a non-volatile memory that can be electrically erased and reprogrammed. In fact, flash memory has undergone an explosive market growth that has in particular been driven by cellular telephones, memory cards, flash drives and other types of portable data storage devices. Indeed, with the need to support persistent data storage in portable devices, it is clear that the flash memory will continue to grow at an ever increasing rate. Further, the market place will demand flash memory designs that support lower cost and higher performance, including higher densities of storage.
An ongoing barrier to reducing cost, improving performance and storage density is yield of the devices. Semiconductor devices are manufactured on wafers (currently 300 mm discs of silicon, which are expected to increase to 450 mm discs in the near future). The wafers are divided into a rectangular grid, and semiconductor devices are fabricated in the rectangles. After fabrication, the devices are tested. If a device fails, it will not be sold to consumers, thus reducing profit for the manufacturer or increasing cost to the consumer. However, if more and more devices are manufactured without errors or defects, more aggressive designs may be pursued, which can provide customers with devices that have higher performance and higher densities.
Improving yield remains an elusive goal.
The features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.